1. Field of the Invention
This invention relates to a method and apparatus for significantly expanding the effective capacity of laser disks, compact disks, digital audio tapes and other conventional digital audio recording media, and more particularly to a method and associated apparatus for multiplexing multiple digital audio signals onto the data channels currently occupied by the pulse code modulated (PCM) digital audio channels on such recording media.
2. Description of the Prior Art
A current standard consumer digital audio format is a two channel stereo 16-bit linear PCM system. This type of encoding is used for compact disks (CDs), laser disks and digital audio tape (DAT), as well as for professional digital tape recorders. It provides two audio channels with somewhat more than 90 dB of dynamic range, and recording times on the order of an hour for a conventional CD. A hierarchy of error correcting techniques are used to detect and correct bit errors, resulting in a system that provides reliable high quality stereo recording.
Although 16-bit linear digital audio provides good quality audio recording, it has not satisfied the very high quality standard desired by audiophiles. New 20-bit analog-to-digital encoders and digital-to-analog decoders have become available, but these devices are not compatible with the 16-bit linear PCM technology used on current CDs and laser disks; the improved quality of the new encoders and decoders therefore cannot be realized with the current digital audio standard.
The limitation of conventional digital audio recording media to two channel stereo and about one hour of recording time is also undesirable. The provision of six channel sound, for example, would create the potential for a listening experience akin to a fully equipped six-track theatrical environment. Furthermore, being able to record significantly more than one hour of sound on a single disk would be beneficial in many cases, while the very rapid disk access capability would still allow any desired portion of the recording to be accessed quickly and conveniently.